Clostridium Questions and Answers

Q: True about clostridium tetani:

Correct answer: Drum stick appearanceC. tetani is a Gram-positive obligate anaerobe carrying a terminal spherical spore that swells the rod into the drumstick shape. Two of the options are true of it - it is Gram positive, and it shows the drumstick - but the drumstick is the distinguishing morphological feature asked for here, the Gram reaction being shared with the whole genus. It certainly does not grow aerobically, and it is not Gram negative.

Q: All are true regarding clostridium tetani except:

Correct answer: Man-to-man transmission is seenThis is the false statement. Tetanus is acquired from the environment, not from other people: spores enter through a wound, and a patient with tetanus is not infectious. It is precisely for this reason that there is no herd immunity and every individual must be immunised. The other three are true - heat-resistant spores, an incubation period usually of six to eleven days, and three primary doses for full protection.

Q: An 18-year old male presented with acute onset descending paralysis of 3 days duration. There is also a history of blurring of vision for the same duration. On examination, the patient has quadriparesis with areflexia. Both the pupils are non-reactive. The most probable diagnosis is:

Correct answer: BotulismThe combination is characteristic: an acute descending paralysis beginning with the cranial nerves, blurred vision from failure of accommodation, and fixed non-reactive pupils from the block of parasympathetic cholinergic transmission. Poliomyelitis gives an asymmetrical flaccid paralysis with intact pupils and usually a febrile prodrome, and Guillain-Barré ascends rather than descends. Pupillary involvement in a descending paralysis points to botulism.

Q: A patient of acute lymphocytic leukemia with fever and neutropenia develops diarrhea after administration of amoxicillin therapy, which of the following organism is most likely to be the causative agent?

Correct answer: Clostridium difficileDiarrhoea beginning after antibiotic therapy, in a hospitalised and immunosuppressed patient, is C. difficile until proved otherwise. The antibiotic suppresses the normal colonic flora, allowing the organism to overgrow and produce toxins A and B. Neutropenia and prior hospital exposure add to the risk. Salmonella and Shigella are community-acquired food and water-borne infections with no such antibiotic association, and C. perfringens causes a brief food poisoning unrelated to antibiotics.

Q: Not true about Botulinum toxin:

Correct answer: Increased acetylcholine releaseBotulinum toxin does exactly the opposite: its light chain is a zinc protease that cleaves the SNARE proteins of vesicle fusion, so acetylcholine cannot be released at the neuromuscular junction and flaccid paralysis follows. That is why it treats blepharospasm, dystonia and wrinkles, and why the option describing an irreversible decrease in acetylcholine is true. The block persists until new nerve terminals sprout, which is why the therapeutic effect lasts some three to four months.

Q: Subterminal spores are found in:

Correct answer: Clostridium sporogenesThe clostridia are classified by the shape and position of the spore. C. sporogenes has an oval subterminal spore, as do C. perfringens, C. septicum, C. novyi and C. histolyticum. C. sordellii and C. tertium carry oval terminal spores, and C. tetani a spherical terminal one that swells the rod into the drumstick. Spore position is one of the first things looked at on a Gram film and narrows the identification considerably.

Q: Most important and potential agent that can be used for bioterrorism.

Correct answer: Clostridium botulinumBotulinum toxin is the most poisonous substance known, effective in microgram quantities, stable, and capable of being disseminated in food or as an aerosol, which is why it heads the list of potential biological weapons and is a Category A agent. Plague and smallpox are also Category A and are serious threats, but neither approaches the toxicity of botulinum toxin per unit mass; tuberculosis spreads too slowly to serve the purpose at all.

Q: Which of the following is NOT appropriate in the management of gas gangrene following a contaminated road traffic accident?

Correct answer: Immediate suturingClosing a contaminated wound immediately is precisely what must not be done: it seals in devitalised tissue and creates the anaerobic environment in which clostridia flourish. Such wounds are debrided, cleaned and left open, with delayed primary closure later. The other three are all part of management - radical surgical debridement of the dead muscle above all, penicillin in high dose, and, in some protocols, antitoxin, though its value is now regarded as doubtful.

41.

True about clostridium tetani:

A.It is Gram +ve
B.Drum stick appearance
C.Grows in aerobic environment
D.It is Gram -ve

Answer: B

Correct answer: Drum stick appearance

C. tetani is a Gram-positive obligate anaerobe carrying a terminal spherical spore that swells the rod into the drumstick shape. Two of the options are true of it - it is Gram positive, and it shows the drumstick - but the drumstick is the distinguishing morphological feature asked for here, the Gram reaction being shared with the whole genus. It certainly does not grow aerobically, and it is not Gram negative.

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42.

All are true regarding clostridium tetani except:

A.Produces heat resistant spores
B.Incubation period 6-11 days
C.Three primary doses of vaccine are needed for full protection
D.Man-to-man transmission is seen

Answer: D

Correct answer: Man-to-man transmission is seen

This is the false statement. Tetanus is acquired from the environment, not from other people: spores enter through a wound, and a patient with tetanus is not infectious. It is precisely for this reason that there is no herd immunity and every individual must be immunised. The other three are true - heat-resistant spores, an incubation period usually of six to eleven days, and three primary doses for full protection.

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43.

True regarding pseudomembranous colitis are all except:

A.It is caused by Clostridium difficile
B.The organism is a normal commensal of gut
C.It is due to the production of phospholipase A
D.It is treated by vancomycin

Answer: C

Correct answer: It is due to the production of phospholipase A

This is the exception. Pseudomembranous colitis is caused by toxins A and B of Clostridioides difficile, which glucosylate Rho GTPases and disrupt the actin cytoskeleton of the colonic epithelium; phospholipase A is not involved. The other three are correct: the organism is carried asymptomatically in the gut of a proportion of healthy people, the disease follows antibiotic disturbance of the flora, and oral vancomycin is a standard treatment.

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44.

An 18-year old male presented with acute onset descending paralysis of 3 days duration. There is also a history of blurring of vision for the same duration. On examination, the patient has quadriparesis with areflexia. Both the pupils are non-reactive. The most probable diagnosis is:

A.Poliomyelitis
B.Botulism
C.Diphtheria
D.Porphyria

Answer: B

Correct answer: Botulism

The combination is characteristic: an acute descending paralysis beginning with the cranial nerves, blurred vision from failure of accommodation, and fixed non-reactive pupils from the block of parasympathetic cholinergic transmission. Poliomyelitis gives an asymmetrical flaccid paralysis with intact pupils and usually a febrile prodrome, and Guillain-Barré ascends rather than descends. Pupillary involvement in a descending paralysis points to botulism.

Discuss in Forum

45.

A patient of acute lymphocytic leukemia with fever and neutropenia develops diarrhea after administration of amoxicillin therapy, which of the following organism is most likely to be the causative agent?

A.Salmonella typhi
B.Clostridium difficile
C.Clostridium perfringens
D.Shigella flexneri

Answer: B

Correct answer: Clostridium difficile

Diarrhoea beginning after antibiotic therapy, in a hospitalised and immunosuppressed patient, is C. difficile until proved otherwise. The antibiotic suppresses the normal colonic flora, allowing the organism to overgrow and produce toxins A and B. Neutropenia and prior hospital exposure add to the risk. Salmonella and Shigella are community-acquired food and water-borne infections with no such antibiotic association, and C. perfringens causes a brief food poisoning unrelated to antibiotics.

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46.

The following statements are true regarding botulism except:

A.Infant botulism is caused by ingestion of preformed toxin
B.Botulinum A, B, E, and F cause human disease
C.The gene for botulinum toxin is coded by bacteriophage
D.Cl. baratii may cause botulism

Answer: A

Correct answer: Infant botulism is caused by ingestion of preformed toxin

This is the exception. Infant botulism is a true infection: spores - classically from honey - are swallowed, germinate in a gut whose flora is not yet established, and produce toxin in situ, giving the floppy infant. Classical food-borne botulism is the one caused by preformed toxin. The other three statements are correct: types A, B, E and F cause human disease, the toxin genes of types C and D are carried on bacteriophages, and C. baratii is among the rarer species that can produce botulinum toxin.

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47.

Not true about Botulinum toxin:

A.Short life span
B.Increased acetylcholine release
C.Used for treatment in Blepharospasm, static and dynamic wrinkles
D.Irreversibly decreases Ach in NM junction

Answer: A

Correct answer: Increased acetylcholine release

Botulinum toxin does exactly the opposite: its light chain is a zinc protease that cleaves the SNARE proteins of vesicle fusion, so acetylcholine cannot be released at the neuromuscular junction and flaccid paralysis follows. That is why it treats blepharospasm, dystonia and wrinkles, and why the option describing an irreversible decrease in acetylcholine is true. The block persists until new nerve terminals sprout, which is why the therapeutic effect lasts some three to four months.

Discuss in Forum

48.

Subterminal spores are found in:

A.Clostridium sordelli
B.Clostridium sporogenes
C.Clostridium tetani
D.Clostridium tertium

Answer: A

Correct answer: Clostridium sporogenes

The clostridia are classified by the shape and position of the spore. C. sporogenes has an oval subterminal spore, as do C. perfringens, C. septicum, C. novyi and C. histolyticum. C. sordellii and C. tertium carry oval terminal spores, and C. tetani a spherical terminal one that swells the rod into the drumstick. Spore position is one of the first things looked at on a Gram film and narrows the identification considerably.

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49.

Most important and potential agent that can be used for bioterrorism.

A.Plague
B.Smallpox
C.TB
D.Clostridium botulinum

Answer: D

Correct answer: Clostridium botulinum

Botulinum toxin is the most poisonous substance known, effective in microgram quantities, stable, and capable of being disseminated in food or as an aerosol, which is why it heads the list of potential biological weapons and is a Category A agent. Plague and smallpox are also Category A and are serious threats, but neither approaches the toxicity of botulinum toxin per unit mass; tuberculosis spreads too slowly to serve the purpose at all.

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50.

Which of the following is NOT appropriate in the management of gas gangrene following a contaminated road traffic accident?

A.IV administration of anti-gas gangrene serum
B.Penicillin
C.Immediate suturing
D.Surgical debridement

Answer: A

Correct answer: Immediate suturing

Closing a contaminated wound immediately is precisely what must not be done: it seals in devitalised tissue and creates the anaerobic environment in which clostridia flourish. Such wounds are debrided, cleaned and left open, with delayed primary closure later. The other three are all part of management - radical surgical debridement of the dead muscle above all, penicillin in high dose, and, in some protocols, antitoxin, though its value is now regarded as doubtful.

Discuss in Forum

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